1. Field of the Invention
This invention relates to vascular balloon catheters which may be used for percutaneous transluminal angioplasty procedures, or alternatively may be used to position and expand a reinforcing stent within a blood vessel. In particular, the invention is especially adapted to treatment of small diameter blood vessels within the brain and may, for example, be used to temporarily occlude a blood vessel to evaluate the results of the occlusion prior to placing a permanent occlusion device within the vessel.
2. Description of the Prior Art
Medical catheters exist for a wide variety of purposes, including diagnostic procedures and interventional therapy including drug delivery, drainage, and perfusion. Catheters for each of these purposes may be introduced to numerous target sites within a patient's body by guiding the catheter through the vascular system. A wide variety of specific catheter designs have been proposed for such different uses.
Of particular interest to the present invention, small diameter tubular access catheters are presently being used for diagnostic and interventional therapy techniques for vessels within the brain, such as the imaging and treatment of aneurysms, tumors, arteriovenous malformations and fistulas. Such techniques place a number of requirements on catheters which are to be employed. The primary requirement is size. The blood vessels in the brain are frequently as small as several millimeters, or less, requiring that catheters have an outside diameter as small as one French (0.33 millimeters). In addition to small size, the brain vasculature is highly tortuous, requiring that catheters for use in vessels of the brain be very flexible, particularly at their distal ends, to pass through the regions of tortuosity. Difficulties in catheter positioning, however, make it desirable to impart high tensile and column strength over at least the proximal portion of the catheter. Additionally, the blood vessels of the brain are relatively fragile, so it is desirable that the catheters have a soft, non-traumatic exterior to prevent injury.
It would therefore be desirable to provide improved small diameter, flexible balloon catheters suitable for introduction to very small blood vessels, particularly to the vasculature of the brain. Such balloon catheters should provide sufficient flexibility to permit access to the tortuous regions of this vasculature, while retaining sufficient tensile, column, and hoop strengths to enhance resistance to kinking and collapse. The improved catheters should also have enhanced positioning characteristics, including pushability and torqueability. Additionally, it would be desirable to have an improved wall strength over a portion or all of the catheter wall to resist bursting and failure when introducing high pressure fluids.
U.S. Pat. No. 4,739,768, describes a catheter consisting of an inner layer and an outer layer, where the inner layer terminates proximally of the outer layer to form a relatively more flexible distal end. World Patent No. 91/17782 describes a catheter having a braid-reinforced distal end with a low friction surface. World Patent No. 93/02733 describes a catheter having four regions of different stiffness. Braid and otherwise reinforced catheter structures are described in U.S. Pat. Nos. 3,416,531; 3,924,632; 4,425,919; 4,586,923; 4,764,324; 4,817,613; 4,899,787; 5,045,072; 5,057,092; 5,061,257; and European Patent No. 555088. U.S. Pat. No. 4.921,478 to Solano et al. shows a cerebral balloon catheter having an open central lumen and a specially shaped balloon.
U.S. Pat. No. 4,976,690 describes a variable stiffness angioplastic catheter in which the stiffness of the catheter is generally controlled by utilizing various catheter wall thicknesses and catheter diameters in order to provide a balloon catheter with a relatively stiff proximal portion and a more flexible distal portion.
U.S. Pat. No. 5,728,065 discloses a balloon catheter in which a flat helical coil is embedded along the length of the inner tubular body of the catheter for providing a relatively stiff proximal portion and in which the turns of the helical coil are spaced apart at the distal portion of the catheter in order to provide for a more flexible distal portion.